The present invention relates to a plastics moulding machine particularly to a protection sleeve adopted between the main driving shaft and the injection ram of the moulding machine.
Several different types of plastics moulding machine have been known in the art, such as compression moulding machines, transfer moulding machines, injection moulding machines, and extruders etc. In earlier stages, the driving and injection mechanism in a moulding machine are connected through gear means and operate in different directions, resulting in a noisy and inefficient operation.
Recently, an improved plastics moulding machine is developed by a Japanese corporation and is shown in FIG. 1. The injection ram of the machine is moved forward and backward without rotation motion. However there are still disadvantages existed such as friction between main driving shaft and the injection ram, the oil ring is easily damaged, and low efficiency in operation.
In FIG. 2, there is shown another type of plastics moulding machines developed by the Nissei Plastics Industrial Co. Ltd. in Japan. The improved machine comprises an injection ram 4 which is driven by the hydraulic system 6 to move forward and backward. The main driving shaft 2 is driven by the motor 1 and connected to the transmission shaft 3, which passes through the injection ram 4 and connected to the screw rod 5. Because the motion of the injection ram is actuated by the hydraulic system, an oil ring is necessary between the main driving shaft 2 and the injection ram 4 to prevent the oil leakage. To the experience of the applicant, there has no such kind of plastics moulding machines which can prevent the oil leakage disadvantages.